Free-piston devices are known, for example, from DE 22 17 194 C3, which corresponds to U.S. Pat. No. 4,154,200. With such devices, chemical energy can be partly converted by means of combustion into mechanical energy, namely kinetic energy of a piston device, and, in turn, this mechanical energy can then be converted via the linear drive at least partly into electric energy. Owing to configuration of the piston displacement as free-piston displacement, a pure linear displaceability of the pistons can be realized without a crankshaft having to be provided.
Corresponding devices can be used, for example, as part of hybrid drives for motor vehicles and, in particular, in conjunction with serial hybrid concepts. They can also be used as compact current-generating units for generating current or in conjunction with stationary applications such as, for example, block-type thermal power stations.
Combustion devices with electric generators are also known from U.S. Pat. No. 6,199,519 B1, DE 31 03 432 A1, East German Patent No. 113 593, DE 43 44 915 A1 or from the article “ADVANCED INTERNAL COMBUSTION ENGINE RESEARCH” by P. Van Blarigan, Proceedings of the 2000 DOE-Hydrogen Program Review.